Speed is a crucial part of many sports, but car racing may be the only one where it's the both the key to victory and a serious threat to survival.

Fans learned that once again last weekend, when two-time Indy 500 winner Dan Wheldon died during a mammoth crash at a race track in Las Vegas.

The risk of death was much higher during the early years of auto racing, when cars traveled at high speeds but didn't have anything near the safety features they do now. Even the fans in the stands were in jeopardy.

But the excitement outweighed the danger during the wild early days of the sport, as author Charles Leerhsen reveals in his 2011 book Blood and Smoke: A True Tale of Mystery, Mayhem and the Birth of the Indy 500.

This week, I asked Leerhsen about the evolution of auto racing, the dangers it posed and the thrills sought by the drivers.

Q: How soon did auto racing begin after the invention of the car?

A: The joke goes that the first auto race started as soon as the second car was made. It began as soon as there was something to compete with: "Mine is better than yours."

Q: Were the races very impressive in the beginning?

A: There was a race in Wisconsin, I think in the 1850s, when they used steam-powered buckboards [a kind of wagon]. They raced at 6 miles an hour, and it was a 200-mile race.

It was totally lacking in spectacle. It was such a success that the second race didn't happen for 17 years.